Mono complexes silicon

Alkyl silyl ethers are cleaved by a variety of reagents Whether the silicon-oxygen or the carbon-oxygen bond is cleaved depends on the nature of the reagent used Treatment of alkoxysilanes with electrophilic reagents like antimony tri-fluonde, 40% hydrofluonc acid, or a boron tnfluonde-ether complex results in the cleavage of the silicon-oxygen bond to form mono-, di-, and tnfluorosiloxanes or silanes [19, 20, 21) (equations 18-20)... 

The range of organo-silicon, germanium, tin, and lead porphyrin complexes reported to date are given in Table Some mono- and dialkyltin... 

The search in recent years for silicon compounds with multiple bonds or cyclic n-systems has renewed interest in siloles (66)77 and their mono- and di-anions (48 and 49), and led to the successful isolation of stable silole anions coordinated to various metal counter ions (Li+, Na+, K+)10a-c 78 - 86 and as complexes with ruthenium (e.g. 6a and 6b)10d. 

Different cyclodextrin monolayers have been synthesized and their surface properties have been characterized. Kaifer et al. prepared per-6-thiol-cyclodextrins, and described the interfacial monovalent ferrocene complexation at the monolayer.55 Mittler-Neher et al. studied the kinetics of the adsorption of mono- and multithiolate-functionalized CD SAMs.56,57 Beulen et al.,58 Huskens et al.,59 Auletta et al.,60 and Nijhuis et al.61 reported on the concept of molecular printboards, that is, (3-cyclodextrin ((3-CD) SAMs on gold or silicon oxide substrates, onto which complementary multivalent guest-functionalized dendrimer molecules were adsorbed, resulting in the formation of kinetically stable supramolecular assemblies. With the... 

The mono-alkoxy product from (+)-ethyl lactate and diisopropylsilane (le) is shown to be more reactive than la and If (Scheme 31). We can only speculate at this time that there may be some intramolecular interactions between the Lewis basic carbonyl oxygen of the (+)-ethyl lactate and the silicon atom, which may either, activate the silane towards oxidative addition to the metal catalyst or increase the rate at which the silane-metal complex is attacked by the nucleophilic alcohol. 

The distinction between between mono- and dinuclear metal complexes is only a formal one in terms of bonding (consider one substituent at silicon the second metal atom instead of an organic group, halide, or hydride substituent). The structural and spectroscopic features related to the three-center bond should therefore be more or less the same as previously discussed. 

Corriu and co-workers in similar mono- and dihalo pentacoordinate silicon complexes.17a 18... 

The reaction of a hydrosilane with ozone results in the rapid, quantitative conversion of the Si-H bond to the Si-OH moiety. The mechanism of this conversion has now been elucidated. It involves a fast, reversible complexation of ozone (acting as a nucleophile) with the silicon atom, followed by rate-determining electrophilic attack by the bound ozone upon the hydridic hydrogen, and decomposition into a RsSi OH radical pair which recombine to produce the silanol. Extensive data concerning the relative rates and other structure-dependent properties in the ozonation of a number of mono-, di-, and trihydrosilanes are presented. 

A convenient method for the preparation of penta- and hexacoordinate silicon complexes was recently developed and reported [1]. The synthesis was based on an exchange reaction between poly-halogenated silanes with the O- or A-trimethylsilylated acylhydrazines and led to the formation of (0-Si)- and (N-Si)- mono and bis- chelate complexes (Scheme 1). 

A number of important review articles have appeared in the area of pentaco-ordinate and hexaco-ordinate phosphorus chemistry. Robert Holmes has provided an extremely informative comparison of the hypervalency, stereochemistry and reactivity of silicon and phosphorus including the application of the latter to enzyme systems. The coordination chemistry of hydrophosphoranes including the formation of complexes from bicyclic-, tricyclic- and tetracyclic hydrophosphoranes has also been the subject of a comprehensive review with literature coverage to 1995. Numerous metal complexes are mentioned including Rh, Ru, Pd, Co, Fe, Mo, and W and the relevance to asymmetric catalysis is discussed. Neutral six-coordinate compounds of phosphorus, including mono-, di-, tri-, and tetracyclic examples, have also been reviewed. 

The di- and tri-fluorides may be obtained by fluorination of the analogous chlorides, Me3P=N SiMe Cl3 ( = 0 or 1), which were obtained independently. The mono- and di-fluorides were monomers, but molecular weight and n.m.r. measurements showed that the trifluoride is a dimer with five-co-ordinated silicon atoms (13). Bis(trimethylphosphazenyl)-dimethylsilane, (Me3P=N)2SiMe2, gives crystalline 1 1 complexes with... 

Type of Active Sites. - In heterogeneous catalysis the following type of actives sites can be distinguished (i) metallic, (ii) acid-base, (iii) red-ox type, and (iv) anchored metal-complex. The catalytic sites may contain one of the above types of active sites or can include several types of sites. In case of different type of sites the catalysts are bifunctional or multifunctional. For instance, Pt/Al203 and Pt/mordenite are typical bifunctional catalysts containing both metallic and acidic types of active sites. On the other hand, Pt or Pd supported on silicon carbide, nitride, or Pt/L-zeolite are mono-functional catalysts. There are important industrial reactions, such as isomerization and aromatization of linear hydrocarbons, which requires bifunctional catalysts, such as chlorinated... 

These observations were rationahzed by the assumption that a pentacoordinate silane is necessary for the cross-coupHng. Both mono- and difluorosilanes are efficient fluoride ion acceptors (from TASF), thereby accessing a pentacoordinate state (Scheme 7.47). The remaining coordination site on sihcon would presumably be occupied by the hahde from the arylpalladium halide complex to allow for a four-centered transmetallation transition state. This last coordination site would not be accessible with a trifluorosilane because it would readily accept two fluoride ions from the promoter, forming an unreactive coordinatively saturated siliconate, and thereby leaving no site for palladium halide complexation. 

Hydroxy acids, such as tartaric, do not form complexes with silicon as they do with the larger germanium atom, according to Clark and Waddams (177), who examined a large number of mono- and polyhydroxy aliphatic acids, including those derived from sugar. 

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